1. Field of the Invention
The present invention relates to laboratory distilling columns and more particularly to a floating ball vapor valve type Snyder column which is free from flooding.
2. Description of the Prior Art
It is often necessary to separate mixtures from one another by distillation in various laboratory techniques. Distilling columns are commonly used for this purpose. In the conventional Snyder column, a vertical glass column is provided having a plurality of indentations around the circumference of the column forming a series of chambers joined by orifices. A hollow glass ball with a downwardly directed stem is disposed inside of the column at each indentation point with each orifice forming a valve seat. As the vapors of the various weight volatiles pass upward through the column, the ball vapor valves will lift allowing the vapors to pass from chamber to chamber. As the heavier fractions condense out, the resulting liquid will flow downward as the ball valves open. This process is known as fractional distillation and is widely used in the KudernaDanish technique as a concentration method for pesticide analysis.
One of the disadvantages of the prior art Snyder columns is a tendency for the balls to stick due to the tight fit of the valve in the orifice. When this occurs the condensing liquid from above will be trapped in the chamber, resulting in flooding. When a prior art valve sticks due to a tight fit in its seat, continuing vapor pressure buildup below may eventually result in a breaking loose of the ball, surging and sputtering of the trapped liquids and possible breakage of the apparatus.
The flooding phenomena is peculiar to Synder columns as well as to a number of types of vertical cylindrical reactors having bubble plate columns. A variety of special designs of the floating ball vapor valves has been tried; for example, in U.S. Pat. No. 4,098,579 to Starzycki, et al, spherical, mushroom shaped, hemispherical, cone shaped, and plate shaped valves are described. However, none of these are effective in preventing flooding due to sticking of the valve in its seat.